The maximum award for 100% loss of use of the leg is 288 weeks. So 15% is 43.20 weeks. (15% x 288 = 43.20.)
Your compensation rate is 2/3rds (no dependents) or 3/4ths (at least one qualifying dependent) of your pay rate for compensation purposes. That pay rate may or may not be the same as your current rate of pay at your Federal job. You probably should convert your annual pay to a weekly pay rate simply by dividing by 52 weeks.
You should be able to come up with a ball park estimate of what you might receive. But, there are other factors that could influuence both your rate of pay and your compensation rate.